Understanding Sea Level Change: A Physics Based Approach

Abstract:

Sea level change is an issue of immense importance in conjunction with global warming. The advent of satellite measurements offers a unique opportunity to address the global patterns of sea level height change associated with global warming. The rate of sea level change, however, is still uncertain due to the relatively short length of the satellite measurements, which began in 1993. In the present study, the contribution of global warming was separated from natural variability via cyclostationary EOF analysis in a sea level reconstruction dataset covering 1950-2010. Global sea level change due to the warming signal is within the range of fluctuations of the global average sea level computed directly from the data but is much less contaminated by natural variability as in the globally averaged sea level heights. A quadratic polynomial fit to the global warming signal indicates that the rate of sea level rise has increased by 0.2 mm yr^-1 per decade and is 1.3 mm yr^-1 as of 2010. The current rate of sea level rise is lower than that estimated from the globally averaged sea level heights by 0.2 mm yr^-1 but is in the 1s range of the estimate (1.3 – 1.8 mm yr^-1).

 Separation of the global warming mode from natural variability allow us to estimate the magnitude of natural variability and the relative significance of sea level change due to global warming. It appears that the sea level change due to global warming is, in general, comparable to natural variability in magnitude so far. Notable exceptions are over the southern tropical Indian, equatorial Pacific, tropical Atlantic, and along the extensions of the western boundary currents. Sea level rise due to warming is expected to exceed several standard deviations of natural variability by 2060 over the majority of the world oceans. This implies that coastal regions will be much more prone to disasters (such as hurricanes) due to warming-induced sea level rise.